The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
The invention relates to a disconnectable turret mooring system for a vessel. Vessels (such as tankers) fitted with a disconnectable turret mooring system are frequently employed in the offshore oil industry. A disconnectable turret mooring system typically allows a buoy to be released from the remaining turret part when environmental conditions may pose an unacceptable hazard to the vessel in which the mooring system is fitted. The buoy is the part of the mooring system that is anchored to the seabed and which supports all risers. Typically, upon release from the remaining turret part, the buoy sinks to a pre-determined level. For again connecting the buoy to the remaining turret part, it is picked up by an appropriate device and again connected with the remaining turret part.
Vessels with disconnectable turret mooring systems are increasingly being employed in deeper water and need to carry an increasing number of risers. This requires a buoy with increasingly large dimensions in order to support the weight of the anchor lines and risers. This in turn also requires the turret structure to be large to be able to receive such a large buoy.
US patent application 2004/0261682 discloses a disconnectable turret mooring system for a vessel, comprising a turret positioned in the moonpool of the vessel and having an upper part cooperating with a first upper bearing assembly positioned between the turret and the vessel, and a lower disconnectable buoy part cooperating with a second lower bearing assembly positioned between the turret and the vessel. The lower bearing assembly according to this document comprises a bearing ring positioned between the buoy and the vessel. This known disconnectable turret mooring system however is not suitable for buoys with large diameter because relatively tight tolerances are required to obtain a reasonable fit between the buoy and the bearing ring. Moreover, to prevent a relative rotation between the buoy and a reaction ring engaging the bearing ring it is suggested to provide means such as pins cooperating with corresponding slots. This makes the structure complicated. Further for ensuring a proper cooperation between such pins and corresponding slots a good alignment during hook up of the buoy is required. Finally, it is a disadvantage of this known mooring system that mounting the lower bearing assembly is complicated.